Need help regarding Brushless Motors,to implement in a fighting robot

hzk17

Joined Mar 20, 2013
31
Updated: As the respected members said and we have discussed not to use Brushless Motors as they cost too much, so we are going to go with Car Window Motors, Now I need your kind advice as which type of Steel or Metal to use to make the body of the robot as its going to fight.

Hello all I have read the theory about BLDCs and all of them Mention a Electronic Speed Controller, what I have read and know that to drive a Motor in conjunction with a Microcontroller you need a Motor Driver Circuit, be it either a Single IC H-Bridge, Relay Based or MOSFETs etc etc, that I know when working with Normal Motors or Brushed Motors but for Brushless do I need some specific circuitry what is this ESC(Electronic Speed Control), I am going to make a Robot for fighting so the design which I found on the Internet uses BLDCs and I read about it so they are really good but that site does not mention all the points only pictures of the complete robot are posted, any help would be appreciated as Me and my group mates will be getting some marks on this Robo.

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Experimentonomen

Joined Feb 16, 2011
331
Given that your robot will likely be more or less destoyed by the other combatants, i'd do it as cheaply as i possibly could, using old brushed motors and cheap pwm speed controllers for dc motors.

Brushless stuff is expensive, too expensive to put into a robot that will be shredded metal nby the end of the day, and smashed remains of what once used to be electronics.

Yes i've seen robotwars and seen ppl's stuff get tore apart well beyond salvage of anything.

hzk17

Joined Mar 20, 2013
31
Can I Use Window Motors, although Modifications would be needed to the body, the original design uses the BLDCs whom shafts are directly connected to the wheels, whereas If I use Car Window Motors, then I cannot remove the gears connected to the motor, so what is your suggestion. @Experimentonomen

GopherT

Joined Nov 23, 2012
8,012
I would stick with the brushless because the weight and space needed for a similarly powered brush motor will not fit in the space and meet the weight. Don't get into combat robots if you cannot afford it. A 30 lb class robot will cost between 1000 and 2000 by the time you have everything.

A one pound bot will be \$300 to 500 to be competitive - including radio, drive motors, chassis, batteries and weapon system.

Here is a speed controller for your bot.

You will need an RC receiver that it can plug into - standard plug connection.

It is not with trying to build your own - brush or brushless.

hzk17

Joined Mar 20, 2013
31
My question is that, is there going to be need of ESC`s, I am using a Mircocontroller with Bluetooth as I am going to give the forward,backward,left,right instructions from my Phone/PC, cant I directly drive the motors using the traditional H-Bridge Circuits.

GopherT

Joined Nov 23, 2012
8,012
First, look at the instructions (rules) from the battlebot organizers. Most require secure channel (digital) radio-receiver pairs. That way a battlebot cannot be accidentally activated and cause major injury. In other words, buletoothe is forbidden.

Google brushless speed controller, Wikipedia or one of the RC sites had a good article on the circuitry. Sensor and sensor less are known. Sensor back-emf is used to determine motor position relative to the magnets so you can apply power to the correct pole and maximize torque. Enable if you are allowed to run bluetoothe, let the bluetoothe module control the speed controller - like the radio receiver would in a normal RC setup.

Two parts to buying one, they are made right electrically and they are durable to survive a crash in an RC plane. Building your own and etching your own board means un-coated copper and oxidation and shorts, ... Just a headache. Finishing the mechanicals will be challenging enough - getting into discrete components will take forever.

#12

Joined Nov 30, 2010
18,210
I use Krylon Clear to coat boards. It isn't the best you can buy, but it will be sufficient for the short term and is removable with the right solvent.

bwilliams60

Joined Nov 18, 2012
1,339
If you are using Brushless motors, they use an ESC to change DC to AC to run the motors. They would probably be 3 phase motors and you need the ESC to perform this function.
As for window motors, they will be much slower although you can really pack a punch with the amount of torque that can be created with one. The outer gear is removable. It may have a steel clip on it that you can bend out of the way to remove it.

http://www.rcuniverse.com/magazine/article_display.cfm?article_id=1344

hzk17

Joined Mar 20, 2013
31
If you are using Brushless motors, they use an ESC to change DC to AC to run the motors. They would probably be 3 phase motors and you need the ESC to perform this function.
As for window motors, they will be much slower although you can really pack a punch with the amount of torque that can be created with one. The outer gear is removable. It may have a steel clip on it that you can bend out of the way to remove it.

http://www.rcuniverse.com/magazine/article_display.cfm?article_id=1344
What I have summarized after the infromation obtained, is that I can design a H-Bridge, and then at its output an ESC is placed, and to that the motors are connected, please confirm, is this the right way to do it.

Papabravo

Joined Feb 24, 2006
14,378
The thing that nobody has mentioned is that the ESC is a closed loop system that measures the RPM of the BLDC motor and does the phase commutation to keep the rotor moving. Hall Effect sensors are a common way to do this and I learned about this method making disk drives. We use a PI (Proportional Plus Integral) controller that maintained 4000 RPM ± a couple of RPM IIRC. The rotor had the magnet and we had an 8-pole drive system(8 coils) on the circular PCB mounted to the rotor. The magnet looked like a doughnut (torus) and also had 8 poles, 4 North and 4 South.